RF pads required for all size nozzles ? 3

[arksurat]

I am making a pressure vessel as per ASME VIII div I for
crude oil seperator. My design pr/temp are 1440 psi / 100 DegC.

I have various size (1" to 6&quot nozzles (seam less pipe) to be attached to this. I want to know if it is mandatory to provide RF pads for all nozzles.

 

[prex]

No.
The use of RF pads is even a second preference with respect to nozzle neck from pipe + flange.
I don't like playing the speaking cricket, but if this is your first project you should look for a tutor or at least have at hand a full worked project of a similar item. prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[ume153]

Hi

As per Sec.VIII Div I only nozzles above 2" (2" not included) should be reinforced. As a good practice 2" (inclusive) and below sized nozzles are stiffened at 90° apart.

 

[Shmulik]

Ume153:
I’m sorry for this comment, but your answer above is NOT correct and misleading. Maybe you didn’t pay attention to the fact that a pressure vessel is life safety equipment, thus, please be so kind and don’t blow that sort of things to the air.
I suggest anyone that do not understand the Code requirements very well, or don’t have the relevant experience: please think twice!

In order to answer the above question you must go over the Code requirements for openings, reinforcing and nozzles:
UG-36 Openings in Pressure Vessels.
UG-37 Reinforcement Required for Openings in Shells and Formed Heads.
UG-38 Flued Openings in Shells and formed Heads.
UG-39 Reinforcement Required for Openings in Flat Heads.
UG-40 Limits of Reinforcement.
UG-41 Strength of Reinforcement.
UG-42 Reinforcement of Multiple Openings.
UG-43 Methods of Attachment of Pipe And Nozzle Necks to Vessel Walls.
UG-44 Flanges and Pipe Fittings.
UG-45 Nozzle Neck Thickness.
UW-14 Openings in or Adjacent to Welds.
UW-15 Welded Connections.
UW-16 Minimum Requirements for Attachment Welds at Openings.
UW-17 Plug Welds.
APPPENDIX L (Mandatory).
APPPENDIX 1-7 Large Openings in Cylindrical Shells (Mandatory).

The above is only to the a.m. question. For design of the entire vessel, please go over the whole book.
Good luck.

 

[jte]

Arksurat-

Ume153 provided a thorough list of Code paragraphs you should glance at, and some you should read thoroughly for nozzle reinforcement issues. For example, chances are that you don't have plug welds on your re-pads, so UW-17 might not be too critical. Appendix L (non-mandatory) provides some good examples and is worth reading.

I'm more concerned about your design conditions. With such high pressure, you should be considering insert plates and integrally reinforced nozzles (even for 2" NPS) rather than re-pads.

Good reading from the Foreward to Div. 1: "The Code is not a handbook and cannot replace education, experience, and the use of engineering judgement. The phrase 'engineering judgement' refers to technical judgements made by knowledgeable designers experienced in the applicatin of the Code."

I'll add my concerns to the others': I'll presume that you have the education refferred to above. If you do not have the experience (and thus do not have the judgement), get a mentor. A vessel at 1440 psi is not a good item for you to begin to gain experience with vessel design.

jt

 

[nassaj]

a message to JTE
I study your interest answer i find you very experience
in design pressure vessle.

tanke you

 

[MJCronin]

aksurat and everyone....

Am I the only one here who suspects a larger problem ??

If someone requests help "making a pressure vessel per ASME VIII" and asks elementary questions, maybe.... just maybe this "vessel" will not be stamped, inspected and tested to ASME VIII?

Do we, as a group, want to encourage fabrication and use of these "homemade" 1400+psig vessels ? ( In the USA, fabrication of high pressure -"homemade" vessels are a violation of state law...)

The only reasonable, responsible answer to questions posed by aksurat is to purchase a coded/stamped vessel from a qualified, certified ASME shop.....@!!!

Anyone disagree with this ????!!!!

MJC

 

[DSB123]

Well said MJCronin,
I agree 100% with your sentiments. Always employ a competent person/company to undertake Design/Manufacture of Pressure systems if catastrophic occurances are to be avoided.
I always think of that old adage "there are those who don't know and there are those who don't knoe they don't know" which is the most frightening??

 

[metaltrade]

i disagree that all vessel purchased should carry an ASME stamp. I do however agree, that all new vessel falling under Section VIII scope should be fab/tested to ASME Code.

I also agree with the opinion of ume153 within the limits stated in ASME.

 

[DavidCR]

After all the above excellent comments (even some are not so accurate, they all give good points to think about). I can add...

The pressure is quite high, don´t dare to do it without experienced knowledge. You could be in a point that integrally reinforced nozzles and FEA would be recommended. (Worst if pressure fluctuations or vibrations are expected.)

When you start to make vessel designs go to the welding shop you think will take care of your jobs, observe the procedures and ask, some design rules about RFs are better understood or even followed "by default" when you see what are the real practices and shop resources. Many times the welding procedures and skill define the type of joint the joint factor, the size of the reinforcement, etc.

ASME reinforcement rules are based on pressure mainly, but external loads on nozzles implies even more complicated and sometimes more important design analysis (WRC 107, FEA, etc.).

Don´t look your vessel just as an ASME code item, look it first with the optic of a more general code or standard that may apply; a local safety code, an API, NFPA, OSHA, Factory Mutual, a construction code, etc. That will clarify if you are able to design PVs. Sometimes you see experts on vessel design that result to be not so expert since they forget basic requirements.

Good luck.

 

[MJCronin]

To all,

Let me restate my point....

Because this case involves the design of a presssure vessel whose failure could involve loss of life, most states in the USA it is mandatory (not a mater of opinion or judgement)that the vessel have an ASME code stamp.

This protects the purchaser as well as the public.

In the past few years, I have noticed an attitude (mostly by middle management) where compliance with the rules of the ASME Boiler & Pressure Vessel Code is a matter "we should take up at the next meeting....." This arrogant diregard of state statutes and laws is the same attitude that causes CEOs to end up behind bars..

These MBA buttholes are the first to promise a client that "a code stamp is not really required" and then look around for someone to blame when there is an accident.

For the small additional cost (about 5 to 7 percent)I dont understand why you would not simply specify an ASME vessel.

Isn't it easier to let the ASME Code certified shop determine the need for RF pads on the vessel.....????

Anyone else out there agree with me ???


MJC

 

[CHD01]

I will add my vote for getting all pressure vessel's CODE STAMPED assuming we are talking about ASME Section VIII vessel's designed for greater than 15 psig. The cost is not that much (but 5-7% seems high to me). Remember, while you may intend for the vessel to be used in a non-code state, it could be salvaged for use somewhere else if given a code stamp initially - in which case you've added to the value of that vessel and increased its potential for re-use elsewhere in-side your corporation.

I would also agree that there is an alarming trend for vessels to be fabricated with a number of errors in design being made (even by the fabricator). While I do not consider my self a true PV expert - none the less I know enough to see the errors made when designers rely on "programs" and then think they are "masters of the universe". At the same time, I think we should be civil in our response to hopefully help people understand the critical nature of PV design without alienating ourselves from them by coming down on them HARD! I notice, the originator of this thread has not responded - perhaps too scared to try? The more you learn, the less you are certain of.

 

[metaltrade]

for those of us who works outside the US of A, the requirement for all vessels design/fab/tested to ASME Section VIII Div 1 need not necessarily be Code Stamped. The decision of whether the vessel should carry a stamped or not is not actually based in the judgement of the MBA but rather a concerted effort of engineers using risk based assessment, part of psm elements, the Code itself, the site-specific standrd and specs, life cycle costing (accepted eng'g practice if i may add), the insurer, etc.

This is on the assumption of course that the operatng facility (perhaps ISO 9000 certified) has a competent resident engineer/s familiar with the ASME, the API 510, RBI, osha 910.11 and FFS and a certified inspector with the full support of the management to ensure that the mechanical integrity of the pressured equipment are maintained. We've cross Y2K, we have matured and both ASME and API are both moving forward.

 

[abbver98]

See UG-36 ( c)(3) for nozzles : no reinforcement is required for :1-3" pipe and smaller in vessel walls 3/8" and less.2-2"pipe and smaller in vessel walls greater than 3/8".
Hope can help

 

[JOHNPIA2]

I agree with all the safety concerns expressed, and to seek advice from a competent design engineer(like myself!). The comments per UG-36(C)3 refer to SINGLE openings, or openings that are spaced apart by at least the sum of their diameters. Otherwise you have to consider LIGAMENT efficiencies. One way to avoid doing nozzle reinfocement calculations is to use FULL RF pads or, use a vessel wall thiclness at lest TWO times the thickness required for pressure. Now, if you have EXTERNAL loads on your nozzles, that is another story!